The present invention relates to a power transmission mechanism that connects a power source to a powered device. More specifically, the present invention pertains to a power transmission mechanism having a disconnection mechanism that cuts power transmission from a vehicle engine to a compressor when an excessive torque load is applied to the compressor of a vehicle air-conditioning system.
Generally, a power transmission mechanism of this kind includes a power transmitter. The power transmitter is located between a rotor located on the engine and a drive shaft of the compressor. When a torque load applied to the compressor exceeds a predetermined value, the power transmitter is deformed and disconnects the power transmission between the rotor and the drive shaft. As a result, excessive torque load does not affect the engine.
However, when the engine is operated at high or middle speed and is suddenly decelerated or stopped, a negative torque can be applied to the drive shaft. That is, when the reduction of rotation speed of the compressor drive shaft is slower than the reduction of engine speed, the compressor seems to be independently operating. This is due to the inertia of the compressor. In this state, the negative torque may disconnect the power transmission mechanism.